1. Field of the Invention
This invention relates to a model engine structure, particularly to an oil collection and forced lubrication structure of a model engine crankshaft.
2. Description of the Prior Art
A conventional model engine, as shown in FIG. 1, includes a longitudinal cylinder 1 installed therein with a piston 2 able to carry out axial motion along the cylinder 1. The piston 2 is provided with a piston rod 3 having one end pivotally fixed at the lower side of the piston 2 and another end stretching downward and jutting out of the cylinder 1 to be pivotally connected with a crankshaft 4, which is transversely assembled at a lower side of the cylinder 2 and extends out of the engine body. Thus, when the model engine is operated, the piston 2 will carry out reciprocating motion in the cylinder 1 and simultaneously, the crankshaft 4 will be driven by the piston rod 3 to rotate and output power produced by operation of the model engine.
The crankshaft 4 has one lengthwise end axially provided with a projecting shaft 5 at a location deviating from the center of the crankshaft 4. The projecting shaft 5 has its radial outer circumferential side fitted thereon with a brass bush 6 to be axially and pivotally connected with the piston rod 3 for operating together. Further, the crankshaft 4 has the face of one end, where the projecting shaft 5 is provided, disposed with a passageway 7 that extends axially along the crankshaft 4 to an intermediate section of the crankshaft 4 and is gradually contracted toward the center of the crankshaft 4, in other words, the inner diameter of the passageway 7 is gradually enlarged toward the end of the crankshaft 4. Furthermore, the crankshaft 4 has one side of its intermediate section bored with a through port 8 communicating with the passageway 7 and has the circumferential wall of its passageway 7 formed with a lubrication hole 9 extending toward the projecting shaft 5 and having its terminal passing through the circumferential walls of both the projecting shaft 5 and the brass bush 6. Thus, when the model engine is operated, mixed oil gas of fuel oil with air will pass through the through port 8 along with the period of cycling of reciprocating motion of the piston 2 and then, the oil gas will pass through the passageway 7 and get into the cylinder 1 to be used by the model engine for operation. And when the oil gas passes through the passageway 7, the centrifugal force produced when the crankshaft 4 is rotated at high speeds will make the oil gas cast outward toward the inner circumferential wall of the passageway 7 and attached thereon. When the oil gas is cast outward along the gradually enlarged inner circumferential wall of the passageway 7, partial oil gas attached on the inner circumferential wall of the passageway 7 will get into the lubrication hole 9 and diffuse to the brass bush 6 in an outward casting process, thus able to produce a lubricating effect to the crankshaft 4 when the crankshaft 4 is rotated.
However, in an operating process of the conventional model engine, when the oil gas passes through the passageway 7, the oil gas that can get into the lubrication hole 9 is very scarce; therefore, when the crankshaft 4 is rotated to push the oil gas to enter the model engine. the axially and pivotally joined portion of the projecting shaft 5 of the crankshaft 4 with the piston rod 3 will bear great damping because of mutual contact and friction in an operating process. As a result, when the model engine is operated, the crankshaft 4 is unable to rotate smoothly, thus influencing the oil gas to enter the cylinder 1 and decreasing efficiency of power output. Even more, when the model engine is operated at high speeds and rotated more than 18000 rpm, the brass bush 6 provided at the pivotally coupled portion of the projecting shaft 5 and the piston rod 3 is likely to be rubbed and damaged. In view of above-mentioned defects, the inventor of this invention thinks that the conventional model engine is necessary to be ameliorated and hence devises this invention.